Coke oven by-products recovery apparatus



NOV. 25, 1941. w LLEN ETAL 2,263,688

COKE OVEN BY-PRODUCTS RECOVERY APPARATUS Filed May 25, 1935 AMMONIALIQUOR,

AMMONIA VAPOR 4 AMMONIA LIQUOR WEAK AMMON LIQUOR SODIUM PHENOLRTEAMMONIA PUMP I MomA, FREE LIQUOR [mentors- JOSEPH W uqcsfluE/v Md 05457lV/LL/IQM SEYL EE.

Patented Nov. 25,1941

COKE OVEN BY-PRODUCTS RECOVERY APPARATUS Joseph Wallace Allen, Clairton,and Hobart William Seyler, Elizabeth, Pa., assignors to Koppers Company,a corporation of Delaware Application May 25, 1935,'Serial No. 23,512'

2 Claims.

This invention relates to the recovery of cokeoven by-products and isprimarily concerned with the. removal of ammonia from weak ammonialiquor so that little or no phenol is driven off with the ammonia orleft in the ammoniafreed liquor.

Equipment is available which removes the ammonia liquor after it haspassed the free leg of the ammonia still, contactsit with steam for therecovery of the phenol contained thereby and returns it to the lime legof the still, the phenol being recovered in the form of sodium phenolateby treating the steam, which recovered it from the liquor, with causticsoda. This recovers some of the phenol but the phenol that escapes fromthe free leg of the still along with the ammonia vapors and/or acidicgases is a loss of suflicient amount to result in noticeable atmosphericpollution should it ultimately be released from the vapor system.

The acidic gases should be removed from the ammonia liquor before itgoes to the phenol removal equipment to avoid the acidic gasesliberating the phenol from the sodium phenolate formed in the phenolremoval equipment and thus interfering with the eflicient recovery ofthe phenol.

The primary object of the present invention is to retard or prevent theabove mentioned escape of phenol and to thereby increase the amount ofphenols recovered when such phenol recovery equipment is used incombination with an ammonia still. Other objects may be inferred fromthe following disclosure.

Having reference to the accompanying drawing, which illustratesequipment of the character under discussion in partially sectionedelevation:

Ammonia liquor is forced by a pump I through a pipe 2 and so into thefree leg 3 of the ammonia still where the free ammonia and/or acidicgases are driven off, these leaving by a pipe 4 which carries them to anunillustrated gas system. The liquor, from which the acidic gases arenow removed so as to avoid the liberation of phenol from the sodiumphenolate in the phenol recovery equipment, is forced by a pump 5through a pipe 6 to dispersers 6 at the top of a chamber 1. As it fallsthrough this chamber it is subjected to the action of steam which iscontinually recirculated by means of a blower 8 and conduit 9, thissteam absorbing the phenols from the ammonia liquor and beingsubsequently subjected to caustic soda which is introduced to it througha pipe l0 and dispersers l0 and which absorbs the phenol from the steamby forming sodium phenolate. The liquor returns to the lime leg I i ofthe still by way of a pipe l2, where it reacts with milk of lime andgoes to the fixed leg l3 of the still through a connection I l Thephenol is subsequently sprung from this sodium phenolate with acid. Thesodium phenolate does not remain in the liquor returned to the lime legof the still but is removed from the chamber 1 by way of an outlet l Thetop of the fixed leg interconnects with the bottom of the free legthrough a connection w so that steam introduced by a pipe 14 to thebottom of the fixed leg also passes through the free leg. Obviously thesteam driving off the ammonia from the fixed leg also drives off thefree ammonia and/or acidic gases from the free leg. The ammonia-freedliquor then leaves the fixed leg through a pipe [5.

The above is described briefly because it is prior art. As previouslynoted, it does not prevent objectionable amounts of phenol escaping fromthe free leg along with the ammonia vapors and/or acidic gases which areleaving through the pipe 4 and are on their way to the gas system.

After careful study the present inventors discovered that considerablymore steam is required to effect the proper driving oiT of the ammoniain the fixed leg than is necessary to remove the ammonia and/or acidicgases from the liquor in its passage through the free" leg. Furthermore,that when sufficient steam is supplied the fixed leg it discharges somuch steam to the free leg that considerable phenol is driven off withthe ammonia and/or acidic gases. These inventors then tried reducing thesteam passed through the free leg by utilization of only that portion ofthe steam from the fixed leg which is required for the removal ofsufiicient amounts of the acidic gases to permit efficient recovery ofthe phenol by the phenol recovery equipment and, at the same time,passing suflicient steam through the fixed leg to also meet therequirements of the latter. The results proved to be excellent, thephenol formerly escaping with the ammonia vapors and/or acidic gasesfrom the free leg being reduced to a satisfactory minimum and,furthermore, being retained in the ammonia liquor which is passed to thephenol removing equipment whereby it can be eiiiciently recovered assodium phenolate.

The equipment illustrated by the drawing includes one example of apractical embodiment of the above discovery. Thus, it is to be notedthat a pipe I6 by-passes steam from the fixed leg [3 around the free leg3 and into the pipe 4. A thermostatically controlled valve I1 isinserted into this pipe with its operating thermal-element inserted intothe top of the free leg and connected to it by a line [8. This valve maybe set to automatically by-pass enough steam to limit the steamdischarged from the fixed still, through the connection I3 to theaforesaid requirements of the free leg, this being done independently ofthe requirements of the fixed leg.

This improvement makes the phenol-removal equipment completelysuccessful in accomplishing its intended purpose.

It is obvious that the valve I! can be operated by the pressure in thefree leg, or to proportionately divide the steam from the fixed leg.Also,

a manually operable valve can be used if automatic operation is notdesired.

The usual Way of determining the loss of phenol by way of the vaporsleaving the free leg is to shut off the phenol recovery apparatus,-

analyze the liquor leaving the still and then operate the phenolrecovery apparatus and determine the percentage of phenol actuallyrecovered. It is obvious that those skilled in the art can easilyregulate the valve I! so as to reduce the phenol loss to a minimum or,to put it another Way, to adjust the valve so as to recover the greatestpossible percentage of phenol by the phenol recovery apparatus.

It follows from the above that the invention is not to be limited to thespecific example shown by the drawing but only by the scope of thefollowing claims.

We claim:

l. Coke-oven by-products recovery equipment including the combination ofan ammonia still having a free leg, a lime leg and a fixed leg whichdischarges steam passed therethrough into said free leg, means forremoving phenol from ammonia liquor after it has left said free leg andbefore it enters said lime leg, and means responsive to vapor conditionsin said free leg for varying the amount of steam discharged from saidfixed leg into said free leg.

2. Coke-oven by-products recovery equipment including the combination ofan ammonia still having a free leg, a lime leg and a fixed leg whichdischarges steam passed therethrough into said free leg, means forremoving phenol from ammonia liquor after it has left said free leg andbefore it enters said lime leg, and means responsive to vapor conditionsin said free leg for by-passing steam discharged from said fixed legaround said 1Tree leg whereby the steam passed through the latter islimited to a determinable amount.

JOSEPH WALLACE ALLEN. HOBART WILLIAM SEYLER.

